Without prejudice to other definitions I would say that a web service is software system that allows for inter-operable machine-to-machine / application-to-application interaction over a network. This generic definitions would also help consider REST architectures to be a web service as they provide similar functionality albeit being an architectural style unlike the SOAP which is a fully defined protocol.

When a registrar registers a com domain name for an end-user, it must pay a maximum annual fee of US$7.34 to VeriSign, the registry operator for com, and a US$0.18 annual administration fee to ICANN. Most domain registrars price their services and products to address both the annual fees and the administration fees that must be paid to ICANN. Barriers to entry into the bulk registrar industry are high for new companies without an existing customer base.[citation needed]
Early image and data storage servers also initially left the uploaded content unchanged, sometimes resulting in undesirable web page display problems, such as too high resolution causing page layout problems in discussion forums, or too high detail causing very slow page loading times. The sharing of potentially incompatible image formats could also result in them not displaying properly for some viewers.
You can build a profile on 500px, and photographers can sell usage of their photos through the site. However, you can’t directly link to photos on other websites. If you’re looking for a platform to upload photos to share on social media or other sites 500px probably isn’t the best option for you. The primary benefit of 500px is the opportunity to display your work and network with other photographers.